A wide variety of prescribed contraceptives deliver small doses of hormones in different combinations. One of four kinds of synthetic progestin provides most of the birth control. To foil conception it thickens cervical mucus to prevent sperm from getting into the uterus, inhibits ovulation, and seems to limit the sperm's ability to move and fertilize the egg. Many products also have one of two types of estrogen, which may help suppress the hormone surge that triggers ovulation and reduce some side effects. (Warning for breastfeeding moms: Estrogen can depress, or dry up, your milk supply.)
Hormonal contraceptives have health benefits, including decreased menstrual cramps and pain and lower risk of endometrial and ovarian cancer, but they may also cause heart attacks, strokes, and blood clots. If a woman takes them exactly as directed, there's a less than 1 percent chance of pregnancy in the first year of use, but the risk with typical usage is 8 percent.
Combined Birth Control Pill
- How it works: With two kinds of formulations, some brands contain the same dose of progestin and estrogen in each pill, while others vary the doses throughout the cycle. Most packs have 21 active pills and 7 placebo, or nonactive pills.
- Advantages: Users experience a quick return to fertility after discontinuing.
- Risks: Nausea, moodiness, heart attacks, strokes, and blood clots. For women with no risk factors, some formulations can double heart disease risk. The risk for smokers can increase 13 times, and smokers over 35 shouldn't take birth control pills.
- Postpartum issues: Wait for six-week checkup.
Extended-Cycle (i.e., Seasonale)
- How it works: Combined pills taken in three-month cycles, 12 weeks of active pills, followed by one week of placebos, causing women to have only four periods a year.
- Advantages: Reduces menstrual-related problems, such as migraines and mood swings.
- Risks: The same as for 21-day-cycle pills. Some women experience spotting and breakthrough bleeding, but this abates over time.
- Postpartum issues: Theoretically the same as the pill; wait for six-week checkup.
- How it works: Contains only progestin, a formula thought to decrease menstrual bleeding, cramping, and anemia. The low-dose pills must be taken at exactly the same time each day. If the interval between pills is longer than 24 hours, cervical mucus thins and lets more sperm through.
- Advantages: Similar to the combined pill.
- Risks: Because it's not widely used, large-scale studies on risks and effectiveness don't exist; the mini-pill has been associated with more spotting and breakthrough bleeding; and other medications can interfere with its contraceptive effect.
- Postpartum issues: If you're nursing, the mini-pill doesn't seem to affect milk supply. Wait until the six-week checkup before taking progestin-only contraception; some experts feel that early exposure to external hormones may interfere with a newborn's own natural hormones.